From: TSS (216-119-163-188.ipset45.wt.net)
Subject: Re: BSE .1 GRAM LETHAL NEW STUDY SAYS via W.H.O. Dr Maura Ricketts [USA MBM/GREAVES IMPORTS] what plan?
Date: February 3, 2003 at 2:47 pm PST
In Reply to: Re: BSE .1 GRAM LETHAL NEW STUDY SAYS via W.H.O. Dr Maura Ricketts [USA MBM/GREAVES IMPORTS] what plan? posted by TSS on February 3, 2003 at 2:43 pm:
ROUND TABLE ON BSE -- WASHINGTON -- 27-28 JUNE 1989
snip...
The summary does tend to give a particular slant to the epidemiology of
BSE which is not totally sound. It is a possibility that the agent of
BSE may be in the cattle population in a number of countries already
apart from the USA and that clinical cases are occurring on rare
occasions. It is also important to off the possibility of the
relationship between BSE and certain low-temperature rendering systems.
For that reason a number of other countries apart from the USA and
France are at risk and, in particular, the Netherlands, Denmark,
Germany and Belgium. For these reasons it would be wise to move to an
international ban on the feeding of ruminant protein to ruminants.
Clearly the summary also needs to refer to the incidence of BSE in the
UK and not solely to Great Britain. No doubt this has been tidied up
in your comments on the summary conclusions. It is a pity that more of
the comments put forward by Dr. Kimberlin have not been included in the
summary since his views on page 13 are succinct and valuable...
snip...
http://www.bseinquiry.gov.uk/files/yb/1989/08/29003001.pdf
Is there a Scrapie-like disease in cattle ?
IN CONFIDENCE
R.F. MARSH
snip...
re-mink rancher 'Wisconsin' dead stock feeder using >95%
downer or dead dairy and a few horses...
http://www.bseinquiry.gov.uk/files/yb/1987/06/10004001.pdf
Part of the Proceedings of an International Roundtable on Bovine
Spongiform Encephalopathy, Bethesda, Maryland, USA, June 27-28, 1989.
The possibility of infection with BSE in the United States, as defined
by studies on the disease in Great Britain, is judged to be low on the
basis of the following: (1) meat and bonemeals imported into the United
States from Great Britain between 1980 and 1988 were used mainly in
poultry, not ruminant feed; (2) the Scrapie Eradication Program had
reduced the prevalence of scrapie in the United States compared with
that in Great Britain; and (3) little, if any, rendered animal products
are used for protein supplements in cattle feed in the United States.
However, there is some evidence that there may already be a scrapie-like
disease in cattle in the United States. This evidence comes from
epidemiologic studies on an incident of transmissible mink
encephalopathy (TME) in Stetsonville, Wis, in 1985. This mink farmer
used no commercially available animal by-product mixtures in his feed,
but instead slaughtered all animals going into the mink diet, which
included mostly (>95%) "downer" dairy cows, a few horses, but never
sheep. To examine the possibility that cattle may have been the source
of this incident of TME, two 6-week-old Holstein bull calves were
inoculated intracerebrally with mink brain from the affected farm. The
bulls developed neurologic disease 18 and 19 months after inoculation.
Both brains had spongiform degeneration at necropsy and both were
transmissible back to mink by either intracerebral (incubation period of
4 months) or oral (incubation period of 7 months) inoculation
Whereas TME has been thought to be caused by feeding scrapie-infected
sheep to mink, this theory has no conclusive evidence. Experimental oral
inoculation of mink with several different sources of sheep scrapie has
never been successful, and an incubation period of less than 12 months
has never (sic) produced by intracerebral inoculation. Transmissible
mink encephalopathy can develop naturally by infection with incubation
periods of less than 12 months.
There is reason to believe that scrapie has not been transmitted in the
United States from sheep to cattle by rendered protein concentrates as
it was in Great Britain. However, some circumstantial evidence exists
that cattle may be a source of some TME infections. It is recommended
that we increase our surveillance for a BSE-like disease in American
cattle by encouraging state diagnostic laboratories to formalin-fix
specimens of midbrain and brain stem from bovine brains submitted for
rabies testing. If results of these tests are negative, these fixed
tissues can then be examined for evidence of spongiform degeneration of
the gray matter.
-Comments on bovine spongiform encephalopathy
J Am Vet Med Assoc 197 (4): (1990)
Letter to the Editor, Journal of the American Veterinary Medical
Association, August 15, 1990
In my article, "Bovine spongiform encephalopathy in the United States"
(JAVMA, May 15, 1990, p 1677), I stated that "little, if any, rendered
animal products are used for protein supplements in cattle feed in the
United States." I have since learned that this is incorrect, because of
the recent trend of using less assimilated "by-pass" proteins in cattle
feed. A large amount of meat-and-bone meal is being fed to American
cattle, and this change in feeding practice has greatly increased the
risk of bovine spongiform encephalopathy (BSE) developing in the United
States.
Epidemiologic studies on BSE in Great Britain have indicated that the
disease originated in cattle by exposure to the heat-resistant
transmissible agent in compounded feed containing rendered animal
protein. The most likely source of infection was assumed to be
meat-and-bone meal prepared from scrapie-infected sheep, but it is also
possible that a heretofore unrecognized scrapie-like infection of cattle
could have been spread in the same manner.
Because of concern for the possible development of BSE in the United
States, the American rendering industry discontinued the processing of
fallen and sick sheep last December. In my opinion, this was a prudent
policy, but one that will not prevent the possible transmission of BSE
from cattle to cattle. As emphasized in my article, there is some
evidence that BSE-like infection may already exist in American cattle.
The current practice of feeding meat-and-bone meal to cattle solidifies
the most important means to perpetuate and amplify the disease cycle.
In Great Britain, BSE has produced a great economic and emotional
burden. We must take all reasonable measures to prevent BSE from
developing in the United States. Therefore, the practice of using animal
protein in cattle feed should be discontinued as soon as possible.
Waiting until the first case of BSE is diagnosed in the United States
will certainly be "closing the barn door after the horse is gone." With
a disease having a 3- to 6-year incubation period, thousands of animals
would be exposed before we recognize the problem and, if that happens,
we would be in for a decade of turmoil.
R. F. Marsh, DVM, PhD
Madison, Wis
TSS
